Oxygen scavenging system

ABSTRACT

The oxygen scavenging system of the subject invention contemplates a composition, system and appurtenant methodology for substantially eliminating elemental oxygen from packaged oxygen sensitive products. The composition or scavenging agent includes an oxidoreductase enzyme, a suitable energy source or substrate for the enzyme, and a buffer. The composition binds oxygen when exposed to moisture, thereby reducing the level of oxygen in a closed (e.g., sealed) space such as a food package or the like. More particularly and preferably, the composition includes glucose oxidase in an amount of between 1 and 100 activity units (U) per gram, catalase in an amount of between 1 and 300 activity units (U) per gram, dextrose in an amount of between about 20 and 99 percent by weight, and sodium bicarbonate in an amount of between about 1 and 80 percent by weight.

This is a regular application filed under 35 U.S.C. §111(a) claimingpriority under 35 U.S.C. §119(e)(1), of provisional application Ser. No.60/389,246 having a filing date of Jun. 17, 2002 and filed under 35U.S.C. §111(b).

TECHNICAL FIELD

The present invention relates generally to oxygen scavenging (i.e.,targeting and reduction/elimination) for oxygen sensitive products, moreparticularly to a composition, system, and attendant methodology forremoving oxygen from stored oxygen sensitive products such as food,pharmaceuticals, etc.

BACKGROUND OF INVENTION

The quality and character of products, whether they be consumables,intermediates, etc., remain of utmost importance. Furthermore, it iswell known that freshness and shelf life can be key or determinativeconsiderations in one's selection calculus. Although degradation is anatural phenomenon and can in fact be desirable, it more often than notis a condition sought to be controlled, more particularly eliminated, orat least slowed down, as is almost always the case with perishablegoods.

Many substances, especially foods, benefit from storage in anenvironment free from, or containing a very low level of, free oxygen(O₂). Oxygen is known to cause oxidative damage to many products,particularly, but not limited too, fats and oils. When exposed to oxygenmany fats and oils oxidize, with a rancid flavor imparted to the fat oroil, other qualities and the general character of the oil being therebyaltered. As the oxidation of fats and oils appears to be aself-catalytic reaction (i.e., upon initiation, the reaction proceedsrelatively quickly, and fully), preventing or retarding the oxidation inthe first place is paramount. Furthermore, and of equal importance, isthe fact that oxygen supports the growth of microorganisms which causespoilage and discoloration of the product.

Current packaging methods and packaging materials enable the eliminationof much of the oxygen via time consuming vacuum and head space gasflushing processes. In most cases, some amount of oxygen remains in thepackage. Removal of oxygen from packages of products where gas istrapped within the product (e.g. bread or pasta) is especiallydifficult. Furthermore, most packaging materials are not impervious tooxygen penetration (i.e., package ingress: over time, oxygen leaksthrough the packaging material, and into the package).

To retard oxidation, anti-oxidants have been added to foods. Forinstance, BHA [(1,1-dimethylethyl)-4-methoxy phenol] and BHT[2,6-di-tert-butyl-para-cresol] are common anti-oxidant food additives.However, BHA is regarded as moderately toxic by ingestion, and eventhough BHT is considered to have low toxicity, the use in foods ofeither of these compounds is limited. While these compounds havecontributed greatly to the food industry by reducing the amount of foodthat must be discarded, some consumers prefer foods without them.

In a broader sense, the binding/scavenging of oxygen has typically beenaccomplished with iron oxide, more particularly, iron oxide packagedwithin gas permeable bags or sachets. Drawbacks associated with suchapproach have included, but are not limited to, careful sealed storageof the sealed package so as to prevent activation upon exposure tooxygen, the expense of such system, and the fact that iron oxide createsheat as it binds oxygen, a less than desirable outcome.

A further, widely practiced means of binding oxygen is the use of theenzyme glucose oxidase, in combination with a suitable glucose source,if necessary. Used alone, glucose oxidase creates or generates peroxide(i.e., hydrogen peroxide is a reaction product). Peroxide may havedetrimental effects on the product in the package and its presence maylimit the further binding of oxygen by the glucose oxidase. The additionof an appropriate amount of catalase enzyme has been used to break downthe peroxide. This works acceptably in many systems where the glucoseoxidase/catalase mixture is spread over a surface, and the packagedproduct acts as a pH buffer, maintaining an acceptable pH range wherethe oxygen binding reaction proceeds, however, efforts to use suchenzymatic formulations in a dispersed or contained form on iron richproducts have been unsuccessful because of discoloration of the product.

It is believed that the lack of success with such enzymatic formulationsis most likely due to the oxygen binding reaction being self-limited bythe change in pH within the bag or sachet (see generally EnzymeTechnology, Chaplin & Bucke, Cambridge University Press, 1990). Asenzymes are amphoteric molecules containing a large number of acid andbasic groups, mainly situated on their surface, the charges on thesegroups will vary, according to their acid dissociation constants, withthe pH of their environment. In addition to the reactivity of thecatalytically active groups, this directly impacts the total net chargeof the enzymes, and the distribution of charge on their exteriorsurfaces. These effects are especially important in the vicinity of theactive sites. Thus, in combination, the variability of the charges withpH (i.e., the charges being a function of pH) affect the activity,structural stability and solubility of the enzyme, and have thus beenlimitations upon this form of oxygen scavenging system.

Although the use of a buffer to stabilize a liquid glucose oxidasesystem during storage is described in European patent EP0418940, it doesnot address oxygen removal or buffering of the system during enzymeactivity. Similarly, U.S. Pat. Nos. 2,765,233 and 5,064,698 teach theaddition to glucose oxidase directly to packaging materials in variousways, namely via encapsulation in polymeric beads. Be this as it may,there are practical limitations on the amount of glucose oxidase thatcan be applied to food wrappers/containers utilizing heretofore knowntechniques. No commercially acceptable oxygen scavenging agent, suitablefor direct application or subsequently introduced post packaging, whichvirtually eliminates (i.e., binds) oxygen present and which furtherinsignificantly changes or modifies the quality or character of theperishable (e.g., does not discolor the item), has been heretoforedisclosed.

SUMMARY OF THE INVENTION

The subject oxygen scavenging system is generally directed to theelimination of oxygen from packaged oxygen sensitive products wheremoisture is present of may become present. An oxygen scavengingcomposition of the subject invention includes an enzyme system (e.g., anoxidoreductase enzyme), a suitable energy source for the enzyme system,and a buffer. The composition, which enhances the shelf-life of apackaged product, is suitable for direct application to the product ofthe packaged product with no consumer detectable change in productcharacter. The composition binds oxygen when exposed to moisture,thereby reducing the level of oxygen in a closed (e.g., sealed) spacesuch as a food package or the like. The system of the subject inventioncontemplates the scavenging composition in combination with a discretewater permeable “housing” within which the composition is contained, oras an integral element or component of a perishable storage container orthe like. More specific features and advantages will become apparentwith reference to the DETAILED DESCRIPTION OF THE INVENTION, andappended claims.

DETAILED DESCRIPTION OF THE INVENTION

The oxygen scavenging system of the subject invention includes acomposition comprising an enzyme system (e.g., an oxidoreductaseenzyme), a suitable energy source or substrate for the enzyme system,and a buffer, the composition scavenging or binding oxygen when exposedto moisture, thereby reducing the level of oxygen in a closed (e.g.,sealed) space such as a food package or the like. Preferably, the enzymesystem includes an oxidoreductase enzyme, more particularly a dryglucose oxidase, and the energy source comprises a reducing sugar, moreparticularly, a glucose source. The composition of the subject inventionpreferably further includes an effective amount of catalase. Forexample, the composition includes glucose oxidase in an amount ofbetween 1 and 100 activity units (U) per gram, catalase in an amount ofbetween 1 and 300 activity units (U) per gram, a glucose source in anamount of between about 20 and 99 percent by weight, and a buffer in anamount of between about 1 and 80 percent by weight. Further still, andpreferably, the glucose source is dextrose, with the buffer preferablycomprising sodium bicarbonate.

As will later be discussed, in addition to the composition of thesubject invention, an oxygen scavenging system is disclosed wherein thesystem includes a water permeable enclosure (e.g., a bag, sachet,laminated sheet, or other three dimensional form) for housing orcontaining the subject composition. Furthermore, in lieu of containment,encapsulation, or general integration with storage media, thecomposition of the subject invention may be formed into solid orsemi-solid three dimensional forms in addition to being directlyintroduced in powder form to, or with, packaged oxygen sensitiveproducts.

Oxidoreductases are enzymes which catalyze oxidation or reductionreactions (i.e., reactions in which hydrogen or oxygen atoms orelectrons are transferred between molecules). This extensive classincludes the dehydrogenases (hydride transfer), oxidases (electrontransfer to molecular oxygen), oxygenases (oxygen transfer frommolecular oxygen) and peroxidases (electron transfer to peroxide). Forexample: glucose oxidase (EC 1.1.3.4, systematic name, β-D-glucose: O₂1-oxidoreductase), or, hexose oxidase (EC 1.1.3.5, systematic name,D-hexose: O₂ 2-oxidoreductase,), each of which will be subsequentlydiscussed.

Glucose oxidase is a highly specific enzyme for D-glucose, from thefungi Aspergillus niger and Penicillium, which catalyses the oxidationof β-D-glucose to D-glucono-1,5-lactone, which spontaneously hydrolyzes,non-enzymically, to gluconic acid, using molecular oxygen, with arelease of hydrogen peroxide as follows:β-D-glucose+O₂→D-glucono-1,5-lactone+H₂O₂

Hexose oxidase, which also functions as an effective oxygen scavengerand is less specific than glucose oxidase, is an enzyme which in thepresence of oxygen is capable of oxidizing D-glucose, and several otherreducing sugars (i.e., substrates) including, but not limited tomaltose, lactose and cellobiose, to their corresponding lactones, withsubsequent hydrolysis to the respective aldobionic acids (e.g., in thecase of D-glucose, gluconic acid). Accordingly, hexose oxidase differsfrom another oxidoreductases (e.g., glucose oxidase) which can onlyconvert D-glucose in that this enzyme can utilize a broader range ofsugar substrates. Hexose oxidase oxidation catalysis may be illustrated,for example for glucose and galactose, as follows:β-D-glucose+O₂→δ-D-gluconolactone+H₂O₂, orβ-D-galactose+O₂→γ-D-galactolactone+H₂O₂The capability of oxygen oxidoreductases, such as glucose oxidase andhexose oxidase, to generate hydrogen peroxide, which has anantimicrobial effect, has been utilized to improve the storage stabilityof certain food products including cheese, butter and fruit juice as itis disclosed in JP-B-73/016612. It has also been suggested thatoxidoreductases may be potentially useful as oxygen scavengers orantioxidants in food products.

As noted with respect to the above enzymatically catalyzed oxidationreactions, hydrogen peroxide is characteristically a reaction productthereof (i.e., most metabolism in the presence of atmospheric oxygenleads to the production of hydrogen peroxide). It is known tocatalytically decompose hydrogen peroxide, and thus eliminate the toxicbactericidal effects thereof, to form water and molecular oxygen,utilizing the enzyme catalase which is derived from the same fungalfermentations as glucose oxidase, as follows:

Catalase

2H₂O₂→2H₂O+O₂For most large-scale applications the two enzymic activities aretypically not separated (i.e., oxygen oxidase and catalase may be usedtogether when net hydrogen peroxide production is to be avoided, andthus inhibition of the oxygen scavenging process by the peroxide).

As to enzymatic activity, it is widely known that the amount of enzymepresent or used in a process is difficult to determine in absolute terms(i.e., mass), as there is an inherent variability in purity, witharguable more relevant parameters being the activity of the enzymepreparation and any contaminating enzymes. A widely known unit of enzymeactivity (i.e., an “activity unit,” U), adopted in 1964 by theInternational Union of Biochemistry (International Union ofBiochemistry. Enzyme Nomenclature: Recommendations 1964 of theInternational Union of Biochemistry. Amsterdam: Elsevier, 1965.), is theamount of enzyme activity which will catalyze the transformation of 1micromole of the substrate per minute under standard conditions.Typically, this represents about 10EE-6 to 10EE-11 kilograms for pureenzymes, and about 10EE-4 to 10EE-7 for industrial enzyme preparations.Another unit of enzyme activity has been recommended, namely, the katal(kat) which is defined as the amount which will catalyze thetransformation of one mole of substrate per second (1 kat=60,000,000 U).Furthermore, non-standard activity units are used, such as Soxhet, Ansonand Kilo Novo units, which are based on physical changes such aslowering viscosity and supposedly better understood by industry.

Suitable energy sources or substrates for the composition of the subjectinvention include carbohydrates (i.e., saccharides), more particularlyreducing sugars (i.e., those capable of reducing a mild oxidizing agent,such as Fehling's reagent). Early biochemists devised analytical methodsfor the detection and quantification of saccharides. One of these test,Fehling's reagent, was based upon the aldehyde (RCOH) or ketone (RCOR)groups present in the saccharide structures: the reagent oxidized thesaccharide while the saccharide reduced the oxidation state of the ionsof the reagent. Generally, saccharides form rings that involve thealdehyde or ketone group. Reversible ring formation is possible unlessthe hemiacetal or ketal hydroxl group has become involved with anotherlink. Rings that are locked have no aldehyde or ketone group to react,unless there are several rings and at least one can open, and arereferred to as non-reducing sugars.

Saccharides may be generally classified as mono-, di-, oligo-, orpoly-saccharides, the fundamental feature being the ability to be eitherdecomposed by hydrolysis, as is the case with the di- andpolysaccharides, or not be decomposed by hydrolysis, as is the case withmonosaccharides. Another feature of saccharides, more particularlymonosaccharides, is that because of their hydroxyl groups (—OH), ringscan be joined together, as by intermolecular dehydration, to formdisaccharides (e.g., a union of α-D-glucose molecules forms maltose).The disaccharides, in turn, may be further dehydrated to join more ringstogether and form polysaccharides (e.g., starting again withα-D-glucose, starch and glycogen may be formed therewith, while startingwith β-D-glucose, cellulose may be formed: the enzymes that hydrolyze βlinkages in cellulose are different from those that hydrolyze alinkages). Typically, in their capacity as reducing sugars,disaccharides reduce half as quickly and half as much as an equal weightof other similar monosaccharides (e.g., maltose/glucose).

Preferable reducing sugars for inclusion in the subject compositioninclude, but are not limited to the monosaccharides glucose, galactose,fructose, xylose, arabinose, mannose, rhamnose; the disaccharidesmaltose, isomaltose, lactose, cellobiose; and, starches (i.e.,polysaccharides) such as amylose and amylopectin.

As previously noted, in addition to the composition of the subjectinvention being placed directly into a package either in contact with,or separate from, the packaged product, bags, sachets, or other formscontaining the composition of the subject invention can be produced andplaced within packages of any moist product where it will consume oxygenwithin or entering the package. After the package is sealed and moisturecontacts the composition of the subject invention, the oxygen levelwithin the package will decrease and will be maintained at a very lowlevel. The quantity of the composition required in a package to achieveand maintain a very low level of oxygen is a function of the amount ofoxygen present in the package when it is sealed, in addition to thequantity of oxygen expected to penetrate the package during the life ofthe package. For convenience, the composition may be placed in a varietyof containers such as bags, sachets, laminated sheets, and numerousthree dimensional forms. The container or enclosure for the compositionof the subject invention needs to be water permeable. It is furthernoted and contemplated that the composition of the subject invention mayalso be compressed or otherwise formed into a solid or semi-solid threedimensional shape for direct placement into packages. Although theoxygen scavenging system of the subject invention contemplates variousmechanisms by which the composition effectively “shares” a head orsimilar space with the packaged product, the critical consideration isthat the composition of the subject invention be placed within or beotherwise integrated so as to be within the package such that it isexposed to moisture.

As to a representative formulation for the composition, namely, onecomprising glucose oxidase, dextrose, catalase and a buffering agent(e.g., sodium bicarbonate), for every mole of dextrose and oxygen actedon by glucose oxidase, one mole of both laconic acid and hydrogenperoxide are produced. Catalase acts on the hydrogen peroxide to produceone mole of water and one half mole of oxygen. The buffering or pHneutralizing agent dampens or counteract the pH reduction caused byformation of the acid. The elimination or mitigation of acid inhibitionof the enzymatic process is especially advantageous for thorough oxygenscavenging. Several different neutralizing agents may be used, but thepreferred buffering agent is sodium bicarbonate because of its pHbuffering capacity, the large carbon dioxide release, and food gradestatus. The molar ratio between the glucose and buffering agent can varybetween from about 0.5 to 1 and 10 to 1, but preferably is 2 to 1.

Initial bench scale tests were conducted by blending one part sodiumbicarbonate to two parts of OxyVac™ (Nutricepts, Inc., Burnsville, Minn.55337) to balance the moles of dextrose and sodium bicarbonate. For theglucose oxidase and the catalase (Amano Enzyme USA Co., Ltd. Elgin,Ill.), one activity unit is defined as the quantity of enzyme that willoxidize 1 micromole of glucose or hydrogen peroxide, respectively, perminute utilizing the prescribed vendor assay method. The testcomposition of the subject invention is characterized as follows:Constituents Effective Amounts Mass (grams) glucose oxidase 3,300 unitscatalase 3,300 units dextrose 65.5 sodium bicarbonate 34   Total: 100Five grams of the aforementioned mixture or composition was introducedinto an emptied tea bag and placed in a heat sealed poly food storagebag containing a moistened paper towel. After approximately 24 hours,the oxygen level in the bag was measured at 0.3 percent utilizingstandard oxygen sensing/indicating apparatus (e.g., Quantek O₂analyzer). At approximately 48 hours, the oxygen level measured 0.0percent.

Thereafter, thirty, 5 gram (g) sachets of the aforementioned compositionwere fabricated using coffee filter material. The filled fiber envelopeswere subsequently pla: in heat sealed poly bags with a variety of oxygensensitive products. The following table summarizes head space oxygenlevels (vol %,) as a function of time, for the listed items: 0₂ LevelItem Temperature 0 24 hours 6 days Water added Ham 40° F. 20% 1.5% 0.0%Summer Sausage 70° F. 20% 4.3% 0.0% Sliced Roast 40° F. 20% 0.2% 0.0%Turkey Fresh packaged 40° F. 20% 4.3% 0.1% Tortellini Shredded Potatoes40° F. 20% 0.2% 0.0% Beef Sausage 40° F. 20% 0.1% 0.1% Damp Paper Towel70° F. 20% 0.0% 0.0%No observable color changes were detected during the aforementionedtests.

In a second test set, the composition of the subject invention wasplaced in direct contact with several of the items previously listed andplaced in heat sealed poly bags. The following results are provided: 0₂Level Item Temperature 0 24 hours 6 days Water added Ham 40° F. 20% 0.0%0.0% Summer Sausage 70° F. 20% 0.8% 0.0% Sliced Roast 40° F. 20% 0.0%0.0% TurkeyA slight color change was noted for the summer sausage after six days.

It will be understood that this disclosure, in many respects, is onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, material, and arrangement of parts without exceeding thescope of the invention. Accordingly, the scope of the invention is asdefined in the language of the appended claims.

1. A dry, organic oxygen scavenging composition for enhancing shelf-lifeof a packaged product, said composition comprising a plurality of dryingredients including an enzyme system, a suitable energy source forsaid enzyme system, and a suitable non-aqueous neutralizing agent forneutralizing acid produced during enzymatic consumption of said energysource and maintaining a stable pH during said enzymatic consumption,said dry, organic composition being suitable for direct contactapplication to the product of the packaged product with no consumerdetectable change in product character.
 2. The dry, organic oxygenscavenging composition of claim 1 wherein said enzyme system comprisesan oxidoreductase enzyme.
 3. The dry, organic oxygen scavengingcomposition of claim 2 wherein said enzyme system further comprisescatalase.
 4. The dry, organic oxygen scavenging composition of claim 3wherein said oxidoreductase enzyme comprises glucose oxidase.
 5. Thedry, organic oxygen scavenging composition of claim 3 wherein saidoxidoreductase enzyme comprises hexose oxidase.
 6. The dry, organicoxygen scavenging composition of claim 3 wherein said suitable energysource comprises a reducing sugar.
 7. The dry, organic oxygen scavengingcomposition of claim 6 wherein said reducing sugar is selected from thegroup consisting of glucose, galactose, fructose, xylose, arabinose,mannose, rhamnose, maltose, isomaltose, lactose, and cellobiose.
 8. Thedry, organic oxygen scavenging composition of claim 7 wherein saidsuitable energy source comprises a glucose source.
 9. The dry, organicoxygen scavenging composition of claim 8 wherein said glucose sourcecomprises dextrose.
 10. The dry, organic oxygen scavenging compositionof claim 9 wherein said oxidoreductase enzyme comprises glucose oxidase.11. The dry, organic oxygen scavenging composition of claim 9 whereinsaid oxidoreductase enzyme comprises hexose oxidase.
 12. The dry.organic oxygen scavenging composition of claim 10 wherein said glucoseoxidase is present in an amount of about 1 and 100 activity units (U)per gram.
 13. The dry, organic oxygen scavenging composition of claim 8wherein said catalase is present in an amount of about 1 and 300activity units (U) per gram.
 14. The dry, organic oxygen scavengingcomposition of claim 13 wherein said glucose source is present in anamount of about 20 to 99 weight percent.
 15. The dry, organic oxygenscavenging composition of claim 14 wherein said suitable non-aqueousneutralizing agent is present in an amount of about 1 to 80 weightpercent of said composition.
 16. The dry, organic oxygen scavengingcomposition of claim 15 wherein said suitable non-aqueous neutralizingagent comprises sodium bicarbonate.
 17. The dry, organic oxygenscavenging composition of claim 14 wherein a molar ratio of glucose tosuitable non-aqueous neutralizing agent is in the range of about 0.5to
 1. 18. The dry, organic oxygen scavenging composition of claim 14wherein a molar ratio of glucose to suitable non-aqueous neutralizingagent is in the range of about 10 to
 1. 19. The dry, organic oxygenscavenging composition of claim 18 wherein said molar ratio of glucoseto suitable non-aqueous neutralizing agent is in the range of about 2to
 1. 20. The dry, organic oxygen scavenging composition of claim 6wherein said composition is contained in a water permeable enclosure.21. The dry, organic oxygen scavenging composition of claim 20 whereinsaid enclosure is a bag.
 22. The dry, organic oxygen scavengingcomposition of claim 20 wherein said enclosure is a resealable bag. 23.The dry, organic oxygen scavenging composition of claim 20 wherein saidenclosure is a sachet.
 24. The dry, organic oxygen scavengingcomposition of claim 6 wherein said composition is contained in laminateproduct receiving structure.
 25. The dry, organic oxygen scavengingcomposition of claim 6 wherein said composition is embodied in a threedimensional form.
 26. A non-aqueous enzymatic oxygen scavengingcomposition in combination with a foodstuff susceptible to oxygenspoilage of a packaged foodstuff, said system comprising an effectiveamount of a dry neutralizing agent for buffering reaction productsformed during enzymatic activity of said system subsequent to directapplication upon said foodstuff in furtherance of oxygen scavenging. 27.An organic oxygen scavenging composition for direct contact applicationto and or with food stuff of packaged food stuffs, said compositioncomprising non-aqueous ingredients, said ingredients including an enzymesystem, an effective energy source for said enzyme system, and aneffective neutralizing agent for neutralizing acid produced duringenzymatic consumption of said energy source and maintaining an effectivepH for continuation of initiated oxygen scavenging.
 28. In a foodpreservation process the steps comprising: a) providing a foodstuffsusceptible to oxygen degradation; b) providing an organic oxygenscavenging composition comprising non-aqueous ingredients, saidingredients including an enzyme system, an effective energy source forsaid enzyme system, and an effective neutralizing agent for neutralizingacid produced during enzymatic consumption of said energy source; and,c) packaging said composition with said foodstuff within a container forsaid foodstuff, said composition thereby in direct contact with saidfoodstuff in said container.